Bridge/extrude/join vertices in a ring
If you want to do this automatically, you can use Bridge Edge Loops by selecting the rings, pressing Spacebar and typing "Bridge Edge Loops":



If you prefer a semi-automatic way, make sure you have F2 addon enabled in User Preferences Ctr+Alt+U > Addons.
Then select 2 vertices using F and continue filling the loop by moving your cursor in the direction you want to create faces and pressing the F (can be pressed repeatedly):